1. Field of the Invention
This invention relates to certain amine and sulfonate group-containing copolymers and their use as backbones upon which to build water-soluble polymeric colorants.
2. Prior Art
Polymeric colorants have been widely studied. Ida et al., Yakugaku Zasshi, 89 (4), 524-30 (1969), were among the first to add polymeric colorants to edibles and show that such colorants are not appreciably absorbed from the gastrointestinal tract into the systemic circulation following ingestion. Such a property potentially eliminates any systemic toxicity which might otherwise arise. Dawson et al., in U.S. Pat. No. 3,920,855, described additional polymeric colorants for edibles. The Ida et al materials were generally formed by joining together a plurality of polymerizable colorant groups into a macromolecule. The Dawson et al materials were formed from polymeric backbones to which were grafted colorant groups. The Dawson et al backbones generally carried amine groups. Gless et al, U.S. Pat. No. 4,018,826, disclosed polyvinylamine as a polymeric backbone for the affixment of colorant groups. The present invention concerns this type of colorant having a different backbone.
In many color-use systems, including the great majority of edible systems, it is essential that a polymeric color be water-soluble. If the colorant group itself is very water-soluble, such as those azo colorants which carry 1 to 4 sulfonate groups, very likely the resulting polymeric color will be soluble as well. However, many attractive colorant groups are not substantially soluble in water. With such groups, water solubility must be imparted by incorporating separate solubilizing groups into the polymer backbone. U.S. Ser. No. 638,730 filed Dec. 8, 1975, now U.S. Pat. No. 4,051,138, by Wang et al. discloses the solubilizing method wherein chromophores are attached to an amine-containing polymer and the polymer is then solubilized by sulfamating residual amine groups. Addition of the solubilizing group should add a minimum of weight and bulk to the colorant if maximum color strength is to be achieved. Likewise, other nonchromophore components, such as the backbone itself, should add minimum weight to the polymeric colorant.
The present invention concerns the use of vinyl sulfonate as a comonomer to impart water solubility to a polymeric colorant. Vinyl sulfonate, ##STR1## is commercially available as the sodium salt. Vinyl sulfonate has been used in the art with added comonomers to form structural copolymers and the like.